With the development of a variety of communication services and portability of communication apparatuses, researches on a cognitive radio technology have been conducted to efficiently use wireless resources.
Generally, in a cognitive radio technology, secondary communication apparatuses of a secondary network cognitively select whole or a part of wireless resources assigned to primary communication apparatuses of a primary network, and use the selected wireless resources.
However, although secondary communication apparatuses communicate using cognitively-selected wireless resources, the secondary communication apparatuses should not interfere with communication operations of primary communication apparatuses. That is, it may be desirable to limit or eliminate interference that occurs in primary communication apparatuses due to secondary communication apparatuses.
Secondary communication apparatuses may need to accurately sense whether primary communication apparatuses perform communication operations, to prevent the secondary communication apparatuses from interfering with the communication operations of primary communication apparatuses. Currently, research is being conducted regarding determining whether the secondary system is performing the communication operation. One scheme, in particular, that sequentially performs a fast sensing operation and a fine sensing operation, is receiving much attention.
According to the above scheme, the secondary system may quickly determine whether a signal received during a fast sensing section exists. The fast sensing section may be a relatively short time period. The secondary system may compare power of the received signal with a predetermined sensing level to thereby quickly determine whether the received signal exists. When it is determined the signal received during the fast sensing section exists, the secondary system may specifically determine whether a signal received during a fine sensing section is transmitted from the primary system. The fine sensing section may be a relatively long time period. The secondary system may specifically determine whether the received signal is transmitted from the primary system using a matched filter and the like.
When a secondary communication apparatus determines that a received signal exists even though a received signal does not exist, a fine sensing may be unnecessarily performed. Also, where a secondary communication apparatus determines that a signal received for a fast time period does not exist even though a received signal exists, the secondary communication apparatus may not perform a fine sensing. Accordingly, a communication operation of a primary communication apparatus is prevented due to the secondary communication apparatus.
Accordingly, there is a need for a technology that may reduce wasting of wireless resources due to an unnecessary fine sensing, and perform a fast sensing more accurately.